The purpose is to determine whether in vitro measurements of lipoprotein lipase (LpL) activity will give us a handle on the in vivo processing of chylomicrons and to determine what levels of remnants would be observed in both heterozygotes and probands. We hope to evaluate patients with lipid abnormalities that correspond to those observed in heterozygotes for LpL deficiency as this would suggest that certain lipoprotein changes in more general populations correlate with changes in LpL activity and/or the LpL gene.